Take 2 at implementing activeTab.

chrome/common/extensions/extension_messages.h

Index: chrome/common/extensions/extension_messages.h
diff --git a/chrome/common/extensions/extension_messages.h b/chrome/common/extensions/extension_messages.h
index 42aab16e12d5cfcbfb4ef791c42cb26a612add36..1573c602534155bc3c45d57c9e256af7dde79ec8 100644
--- a/chrome/common/extensions/extension_messages.h
+++ b/chrome/common/extensions/extension_messages.h
@@ -125,6 +125,9 @@ struct ExtensionMsg_Loaded_Params {
   URLPatternSet explicit_hosts;
   URLPatternSet scriptable_hosts;
 
+  // The extension's tab-specific host permissions.
+  std::map<int, URLPatternSet> tab_specific_host_permissions;
+
   // We keep this separate so that it can be used in logging.
   std::string id;
 
@@ -238,6 +241,10 @@ IPC_MESSAGE_ROUTED1(ExtensionMsg_GetApplicationInfo,
 IPC_MESSAGE_ROUTED1(ExtensionMsg_UpdateBrowserWindowId,
                     int /* id of browser window */)
 
+// Tell the renderer what its tab ID is.
+IPC_MESSAGE_ROUTED1(ExtensionMsg_SetTabId,
+                    int /* id of tab */)
+
 // Tell the renderer to update an extension's permission set.
 IPC_MESSAGE_CONTROL5(ExtensionMsg_UpdatePermissions,
                      int /* UpdateExtensionPermissionsInfo::REASON */,
@@ -246,6 +253,18 @@ IPC_MESSAGE_CONTROL5(ExtensionMsg_UpdatePermissions,
                      URLPatternSet /* explicit_hosts */,
                      URLPatternSet /* scriptable_hosts */)
 
+// Tell the renderer about new tab-specific permissions for an extension.
+IPC_MESSAGE_CONTROL4(ExtensionMsg_SetTabSpecificPermissions,
+                     int32 /* page_id (only relevant for the target tab) */,
+                     int /* tab_id */,
+                     std::string /* extension_id */,
+                     URLPatternSet /* host */)
+
+// Tell the renderer to clear tab-specific permissions for some extensions.
+IPC_MESSAGE_CONTROL2(ExtensionMsg_ClearTabSpecificPermissions,
+                     int /* tab_id */,
+                     std::vector<std::string> /* extension_ids */)
+
 // Tell the renderer which type this view is.
 IPC_MESSAGE_ROUTED1(ExtensionMsg_NotifyRenderViewType,
                     chrome::ViewType /* view_type */)